Machine tool transmission mechanism



0a; 13, 1959 J. B. ARMITAGE ET AL 2,908,178

' MACHINE TOOL TRANSMISSION MECHANISM Original Filed Jan. 19, 1950 I 5Sheets-Sheeti Jf'lfarney .O ct. 13, 1959 J. B. ARMITAGE ET AL v2,903,178

MACHINE TOOL TRANSMISSION MECHANISM Original Filed Jan. 19, 1950 5Sheets-Sheet 2 Oct. 13, 1959 J. B. ARM'ITAGE ETAL 2,908,178

' MACHINE TOOL TRANSMISSION MECHANISM Original Filed Jan. 19, 1950 v 5Sheets-Sheet 3 TI'ORNEY Oct. 13, 1959' J. B. ARMITAGE ETAL 2,998,178

1 MACHINE 'roor. TRANSMISSION MECHANISM Origizial Filed Jan. 19, 1950 5SheetS-Sh'eetS )NVENTQRS J b .flrmnage, James A. 9/annery v .ZJMAZ /0779llorney United States Patent C) MACHINE TOOL TRANSMISSION MECHANISMJoseph B. Armitage, Milwaukee, and JamesN. Flannery,

West Allis, Wis., assignors to Kearney & Trecker Corporatlon, WestAllis, Wis, a corporation of Wisconsin Original application January '19,1950,. Serial No. 139,342", now Patent No. 2,736,243,. dated'.February-28, 1956. Divided and this application June 13, 1955, Serial No. 515,177

11 Claims. 01. 74 sss Another object is to provide animproved speedchanging transmission. mechanism for a milling machine adapted totransmit full torque at high output speeds while being adjustabletotransmit only low torque atlow output speeds.

Another object is to provide a milling machine of improved constructionhaving a tool spindle disposed to be driven at a wider than usual rangeof output speeds.

A still further object is to provide an: improved power transmissionsystem for a machine tool, including a pair of range change mechanismsconnected in series relationship and arranged to be driven by a fixedstep speed changer, the mechanisms being so proportioned as. to providefor continuous speed changes throughout their full range of operationand one of the range change mechanisms being operable to provide anextremely low series of output speeds.

According to this invention,. a machine tool such as a milling machine,is provided with a high powered motor operatively connected to drive atool spindle with relatively high torque at high rates of speeds forfaster removal of metal from a workpiece. A cooperating work supportingmember is disposed to be. selectively driven along three mutuallytransverse lines of movement by means of a separate work feeding motorthat is electrically interconnected with the spindle driving motor. Todrive the tool spindle at any selected speed within a wider than usualrange of operating speeds, an iniproved variable speed transmissionmechanism is operatively interposed between the spindle driving motorand the tool spindle.

The foregoing and other objects of the invention which will become morefully apparent from the following detailed description of apparatusexemplifying the invention may be achieved by the milling machinedescribed herein as a preferred embodiment thereof in connection withthe accompanying drawings, in which:

Figure 1 is a view in perspective depicting the left side of a millingmachine of the knee and column type incorporating a preferred form ofthe invention;

Fig. 2 is a vertical longitudinal sectional view through the upper pareof the machine, showing the spindle driving transmission mechanism;

Fig. 3 is a vertical longitudinal sectional view through ice 2 the upperpart of the machine, showing a modified form of spindle drivingtransmission mechanism; 7

Fig. 4 is an enlarged fragmentary vertical transverse sectional viewthrough the upper part of the machine, showing the speed controllingapparatus for the spindle driving transmission mechanism; v

Fig. 5 isa vertical longitudinal sectional view taken on the line 55 ofFig. 4 and showinga portion of'tlie speed controlling apparatus; and,

Fig. 6 is a horizontal. sectional view taken on the line 66 of Fig. 5andv showing a portion of the speed con trolling and power transmittingmechanisms.

Referring more particularly to the drawings and especially to Fig. 1thereof, the machine tool there shown as an example of apparatusconstituting a preferred embodiment of the. invention, is a millingmachine of the well known horizontal spindle type generally similar inoverall structure to the machine more fully shown and described in.United States. Patent No. 2,497,842, which issued on February 14,.19-50. As shown in Fig. 1{ of the drawings, the milling machinestructure comprises essentially an upstanding column 1 2 which serves tocarry on its face a knee 1-3, saddle 14, and work supporting table 15superimposed; for selectively slida'ble movement in a plurality ofmutually transverse planes. Near the top of the column 12 there is'journa-lled the usual horizontally'di'sposed tool supporting spindle 16and above it are slidably mounted overarmsi 17 for supportinga cutterarbor (not shown) that may be mounted in the spindle 16 in well knownmanner to carry a cutterin cooperating relationship with a workpiece onthe Work supporting table 15.v

Power for rotating the tool spindle 16 is derived from a: relativelyhigh powered motor 18 that is mounted in a motor compartment 19 formedwithin and extending transversely of the lower part of the column 12.The speed at which the spindle 16.- is operated may beadjusted by meansof a. range change lever 20 and aspeed selecting. lever or crank 21mounted on the left side of the column 12, the levers. functioningcooperatively to shift speed changing gearing mounted within the column12, directly above but separated from the motor comipartment 19. Thespindle speed is. indicated by the co ordinated positioning of a pair ofrange change indicating plates 22 and 23 associated with the rangechange lever 20, in cooperation with a speed indicating dial'Zlthat isconnected to-beturned by the crank21-..

As fully explained. in the. aforementioned parent patent application,SerialNo. 139,342, now Patent No. 2,136,243., power for effectingmovement of the vertically slidable knee 13, the transversely slidablesaddle 14v and the longitudinally slidable table 15 is derived from aseparate feed motor not shown) mounted on the rightward. side of theknee 13 and arranged to be operated coordinately with the relativelyhigh powered spindle driving motor 18. In order to effect selectivedirectional movement of the knee 13, saddle 14, and table 15, there areprovided at the front of the machine, as shown in Fig. 1, directionalshifting levers 2,6, 27 and 28 operatively connected to actuatereversing clutch mechanisms for transmitting power to drive therespectively movable members.v To minimize lateral deflection of theknee 13 and provide maximum rigidity for the work supporting table 15during a cutting operation, there is provided an improved elevatingmechanism for the knee, and which is: arranged to be actuated undercontrol of the directional shifter lever 26. For effecting selectivefeeding movement of the Work supporting table 15 relative to the cutterspindle 16, there is provided on the front of the knee a feed rateselecting lever 30 connected to shiftably adjust. a variable speed,'feedtransmission contained in a gear compartment formed within the base 13.In. order to efiect movement of the .knee 13, saddle 14 or table 15 at afast or rapid traverse rate of speed, a rapid traverse lever 31 isconnected to effect energization of the feed motor 25 and 1simultaneously therewith to actuate a clutching mechanism (not shown)vtoeffect transmission of power .toflriVeeech of the reversing mechanismsrespectively engageableon movement of the feed directional levers 26,27and28. r e

For effecting coordinated energization of the spindle driving motor 18and the feed motor (not shown), a

' control station 32 mounted on the left side of the column is providedwith'controlling means for coordinately starting or stopping the spindlemotor 18 and the feed motor,

, I *4" a parts of the intermediate idler cluster: 60. The sliding gears65 and 66 constitute .a secondary element of the speed changingmechanism A and may be selectively as well as inching control meansarranged to effect a momentary energization of'the spindle drivingmotor, as fully explained in the aforementioned parent patentapplication, now Patent No. 2,736,243.

, Referring now to Figs. 2 and 4 of the drawings, 'power the machinecolumn and isconnected to transmit power tov arshaft 35 which extendsinto the column and has integrally formed with it a driving bevel gear36. The

driving bevel gear 36 transmits driving powerto a meshing'drivenbevelgear 37 which is journalled to rotate on one end of a. shaft 38. Theshaft 38 is rotatably journalled in a speed box 39 which extends withina gear compartment 40 above the motor compartment in the column throughan opening in the left side thereof. As shown in Fig, l, a cover plate 7or control panel 41 supports the speed box 39 within the'colum'n openingand carries the range change lever and the speed selecting crank 21,"aswell as the range change indicating plates 22 and 23 and thespeedindicating'dial 24 respectively associated therewith for indicating theselected driving speed of the spindle 16.

Referring again to Fig. 2, the driven bevel gear 37 is integrally formedwith an elongated spur pinion 45 which meshes with one gear 46 of acouplet 47 that is slidably mounted for selective longitudinal movementon a short .of two speedratios;

positioned to transmit driving power from the intermediate idler cluster60 to thesplined sleeve64 at either ,-Since the primary element of thevariable speed device A constituted by the couplets 47 and 49.is capable of .four different speed rates and the secondary elementconstituted by the gears 65 and .66 is capable of two speed rates, it isevidentthat the splined sleeve 64.may be driven atanyone of eightspeeds, by suitably-engaging different ones of the sliding gears in theprimary and secondary elements with their cooperatingidler gearsconstituting the intermediate speed transmitting idler cluster 60.Asindicated in Fig. 2, the gears are shown in position to drive thesplined sleeve 64 at the lowest speed rate of the eight speeds availableithroug'h' the speed changing device A with the large gear 66 of thesecondary element engaging the small idler gear 59 and thevsmall gear 56of the primary element engaging the large idler gear 58. As Willhereinafter be more fully explained, the speed selecting crank 21. and'the indicating dial- 24 are movable to a plurality of positions.

nalled on the shaft62, power is transmitted through an intermediaterange changing mechanism B to drive 'the rotatably journalled shaft 62in a selected one of two speed rate series. Power is then transmittedfrom the shaft 62 through afinal range changing mechanism C splinedshaft 48 parallelly journalled in the speed box 39. The splined shaft48, together with the'gear couplet -47-and a second gear couplet 49slidably carried by the shaft for longitudinal shifting movement,constitute ele- -ments' of. a speed changing device A forming one partof 'the speed changing transmission mechanism. The couplet 47 comprisesthe gear 46 and a gear 50 joined together and disposed to be selectivelymeshed alternatively with cooperating idler gears 51 and 52,respectively, rotatably journalled on an idler shaft 53 that is fixedlymounted within. the speed box 39 above and parallel to the ro- 'tatablyjournalled splined shaft 48. The second couplet 49 slidably mounted onthe splined shaft 48, comprises a gear 55 and a gear 56 joined togetherand disposed to be selectively meshedalternatively with a gear 57 and agear 58, respectively, also journalled on the shaft 53. The.

four idler gears 51,52, 57, and 58 together with a gear 59 journalled onthe stationary shaft 53, are secured together in manner to rotate as oneunitary intermediate idler cluster 60 of the speed changing device A,The two couplets on the shaft .48 constituting the primary element ofthe speed changing device A may be shifted 'to engage each of the fourgears in turn with its comple- 'm'entary idler gear on the shaft 53 todrive all of the idler gears constituting the idler cluster 60 at anyone of four different rates of speed.

Above the stationary shaft 53 'and disposed parallel to it is a longershaft 62 that is journalleddirectly. in the column 12 and that inturnhas rotatably journalled on its central portion 63 an externallysplined sleeve 64.

' Slidably mounted on the splinedsleeve 64 are shiftable gears 65 and 66which are selectively slidablel to mesh --w1th the idler gears 52 and59, respectively, which form which functions to deliver power to thetool spindle 16 in a high or a low operating range alternatively. The

intermediate range changer B and the range changer C between the ranges.

,A gear 71 rotatably journalled on the central portio of the shaft 62 issecured to thesplined sleeve 64 in manner to transmit driving powertherefrom to a meshing gear 72 secured to a jack shaft 73 rotatablyjournalled 'in the column 12 in parallel relationship with the shaft 62and constituting an element of the intermediate range changing mechanismB. The primary element of the intermediate range changing mechanism isconstituted bya gear 74 which is slidablymounted on a splined rear-.ward portion of the shaft 62 for selective longitudinal shiftingmovement thereon. .Asshown in Fig. 2, the gear 74 has been shiftablypositioned to engage a'comple- 'mentar'y gear 75 secured to the jackshaft 73 in a manner to transmit driving power from the gear '71;through the gear 72 and the jack shaft 73 to drive the spindle'drivingshaft 62 in an extremely low range of speeds. With this 7 conditionexisting, it will be apparent that the shaft '62 is connected to berotatably driven at a much lower rate'rof speed than the sleeve 64 andgear 71 which are rotatably journalled in the central portion of theshaft. For driving the shaft 62 in a higher speed range, the gear 74 maybe moved rightwardly in manner that an internal gear 76 formed thereindirectly engages the teeth of the gear -71 in the manner of a clutch.

From the'shaft 62, power is transmitted through a couplet 78 slidablysplined on the rightward end 79 of the shaft 62 and constituting thefinal range changing mechanism C which is arranged to drive the toolspindle 16 in a high or a low range of operating speeds. The

QQI1P1L78 comprises. a small gear 80.- and a large gear 81 joinedtogetherand mounted for longitudinal sliding movement on the shaft 62into meshing engagement alternatively with a low range driving gear 83or a :high range driving gear 84, respectively, which are splineddirectly to the Spindle 16.

As hereinbefore mentioned, the gears of the intermediate range changer Band the range changer C are positionable in a plurality of positions fortransmitting driving power from the splined sleeve 64 to rotate thespindle 16 at any one of three distinct speed ranges including a low,intermediate and a high range. To drive the spindle 16 through thelowest range of operating speeds, the range changers B and C arepositioned as I shown in Fig. 2, with the gear 74 engaging itscomplementary driving gear 75 and the gear 80 of the couplet 8 engagingits complementary low range spindle driving gear 83; For driving thespindle 16 through an inter- ;mediate range of speeds, the gear 80 ofthe couplet 78 is .;retained in meshing engagement with the low rangespindle drive gear 83 and the gear 74 is shifted rightwardly in mannerthat the internal gear 76 formed therein engages the complementary gear71 thereby locking the sleeve 64 to-the shaft 62. Thus, in the low andintermediate ranges constituting the lowest sixteen speeds, drivingpower is transmitted from the small spindle driving gear 80 to the largespindle driving gear 83. To drive the spindle 16 'at the high range ofoperating speeds, the gear 74 is retained in its rightwardly shiftedposition in clutching engagement with the driving gear 71 and thecouplet 78 is shifted leftwardly in manner that the gear 81 is inmeshing engagement with the high range spindle driving gear 84. Thelarge gear 83 has the efiect of a flywheel and tends'to reduce to aminimum minor fluctuations in cutter speed which might occur as theindividual teeth of a cutter engage a workpiece. During the intermediateand high ranges of output speed, the internal gear '76 is retained inengagement with the gear 71 for driving theshaft 62 at the same speed asthe sleeve 64.

The speed changing device A functions to provide a series of eightdifferent driving ratios in step by step arrangement within each of thethree distinct speed ranges effected by the combined positioning of therange changers B and C and including a low, intermediate and'high speedrange so proportioned as to provide progressive steps withoutoverlapping or discontinuity between the ranges. By this combination ofthe speed changing device A with the intermediate speed range changer Band the range changer C, it is possible to predeterminately position theshiftable gearing contained therein for operating the tool spindle 16 atany one of twenty-four speeds arranged in approximate geometricalprogression.

' A principal advantage of the improved variable speed transmissionmechanism illustrated in Fig. 2, is the provision of a wider than usualrange of output speeds effected by arranging the transmission to have agraduated power transmitting capacity in a manner to transmit the fullpower of a relatively high powered spindle driving motor at the higherrates of speed. Generally, in variable speed transmissions of thes-hiftable gear type, there is a definite limitation in the overallrange of allo able output speeds, particularly when a relatively highpowered constant speed motor is utilized as a source of power. Includedamong the main factors determining the upper and lower limits of theallowable range of output speeds are the input power of the drivingmotor, as well as the space allowable for a transmission disposed, to beselectively adjustable for transmitting as many output speeds aspossible within a selected range.

As is well known in the art, an inherent characteristic I as thetransmission is adjusted upwardly to drive a tool spindle at higherrates of speeds, the torque on the various movable members thereof willbe decreased.

Until recent years, when improvements in cutting tools necessitated aconsiderable increase in spindle driving power, the power required torotate a cutter spindle for removing metal from a workpiece withmaximum. efficiency has been considerably less than is now required inutilizing the improved methods of performing a cutting or machiningoperation. Thus, with. the lesser requirements of spindle driving powerin prior types of machine tools, the variations in torque effected as ashiftably geared spindle driving transmission was adjusted through acomplete range of driving speeds imposed no serious load conditionstending to exceed the power transmitting capacity of the transmission.In a milling machine of a specified size therefore, the transmissionmechanism could be so arranged as to provide as wide a range of spindledriving speeds as necessary while transmitting the full power of thespindle driving motor for driving the cutter spindle with maximumefficiency in performing a cutting operation on a workpiece suited tothe size and-capacity of that particular machine.

With the advent of improved techniques in the utiliza-' tion of millingmachine cutters and the attendant increase in the rate at which metalcould be removed from a workpiece, however, the variations in torque onthe various rotatable members of a variable speed transmission mechanismimposed a serious restriction on the allowable range of spindle drivingspeeds. With the available input driving power for the cutter spindletrebled or quadrupled, for example, to more fully utilize the improvedmethods of removing metal from a workpiece, it was necessary tostrengthen the various rotatable members of a shiftably geared spindledriving trans-mission mechanism to effectively transmit the full powerof the driving motor through a selected range of speeds. The overallrange of output speeds however, was necessarily restricted and did notprovide for an extremely low series of spindle driving speeds because'of the excessive torque developed, in the event the full capacity ofthe higher powered motor were applied. Inasmuch as a milling machine isusually so proportioned as to accommodate a range or class of workwithin the power capacity of the motor when the spindle is driven at thehigher rates of speeds, there are structural and economic limitationspreventing the construction of a variable speedtransmission havingsufiicient capacity to transmit the full power from a relatively highpowered motor at extremely low rates of speed.

A primary advantage of this invention is the provision of a compactlyarranged variable speed transmission having operating characteristicsthat provide for transmitting the full power of the relatively highpowered driving motor to drive the tool spindle with a higher degree oftorque than has heretofore been practicable, for faster'removal of metalat the high speed rates. In addition to this, the transmission is soarranged as to be selectively adjustable through a wide range of spindledriving speeds extending downwardly through a series of extremely lowoperating speeds in manner to increase the operational flexibility ofthe machine for performing the largest possible variety of cuttingoperations. The transmission is necessarily limited in its powertransmitting capacity at the lowest output speeds because of thebefore-mentioned limitations imposed by the overall size and capacity ofthe machine, the extremely high powered spindle driving motor and thevariations in torque on the various rotatable members of any shiftablygeared transmission which occur as the output'speed thereof is eifectedin predetermined order. tion of the crank 21 is required for each gearshifting selectively adjusted through its complete. range ofallowable'speeds. .In normal machine operation however, this .power ofthe relatively high-powered spindle driving mo- 'tor 1 8 Whenever thetransmission is adjusted to drive the tool spindle 16 at a selectedspeed in either the high, the "intermediate or portions of the low speedrange. When the transmission is adjusted to drive the spindle 16 withinI: the lowest rangeof'operating speeds however, it will be apparentthatthe mechanical advantage eifected by en- I'gaging the intermediaterange change gear 74 with the low speed driving gear 75 will greatlyincrease the torque on the low speed driving gear 80 and its meshingspindle 1 gear 83 if the full power of the motor were applied at thelowest driving speeds. With the gear 74 engaging the gear 75 todrive thespindle 16 through the lowest operating range, the greatest mechanicaladvantage, and, consequently, the 'highest torque on the spindle drivinggears would occur during the lowest of the eight stepped driving ratiosobtainable by selectively shifting the gearing in the speed changingdevice A. As a result of the in- 1 creased mechanical advantage on thespindle driving gears 80 and 83, thepower transmitting capacity of theentire variable speed transmission mechanism is reduced in the lowest ofthe eight stepped speed ratios available in the a low range.

Although the transmission mechanism shown in Fig. 2

iis of the variable torque transmitting type, a principal advantage ofthe invention is the novel arrangement for providing an extremely widerange of output speeds.

To protect the transmission mechanism against varying degrees of torquewithin the range of its torque transmitting capacity, there is provideda preferred form of adjustable torque limiting control, as fullydescribed in the aforementioned Patent No. 2,736,243.

I The control mechanism for shifting the various sliding 1 gear coupletsand gears to effect the changes in the spindle driving ratio is similarto that disclosed. in U.S. Patent No. 7 2,240,973, dated May 6, 1941. acam actuated gear shifting apparatus constituting a mechanical linkagearranged to be directly operated by the fspeed selecting crank 21 andfunctioning to positively I shift the sliding gears of'the variablespeed device A in This mechanism includes such a manner that the eightspeeds of the series may be movement of the speed changing device A or atotal of eight revolutions of the crank are required to effect acomplete transit of the eight stepped driving ratios availabletherethrough. In order to obtain the complete series of twenty-fourspindle driving speeds available with the combined coordinatedpositioning of the speed changing device A and the range changers B andC, a total of twenty-four revolutions .of the crank 21 are required.Coordinately with the three repetitive series of shifting movements ofthe speed changing device A, the crank 21 is operatively connected toeffect a coordinated shifting movement of the intermediate rangechanging mechanism B. The shifting mechanism operative on movement of .Ithe crank 21, is so arranged that the gears are shifted in a manner toavoid possibility of locking the mechanism .by engaging more than onegear on the primary shaft 48 I I or more than one gear on the secondaryelement 64 with I a cooperating gear .of the idler cluster 60, and in amanner 1 that the intermediate range change gear 74 is in its low rangedriving position during the first of the three repetil .tive series ofshifting movements of the speed changer A, awhile forv the lasttwoseries of shifting movements of the speed changerA, the gear 7 isretained in engagement with the gear 71 for its high range'drivingposition'.

" 90. The pinion 90, in turn, meshes with a gear 91 formed 7 on theperiphery of. a primary speed changing cam 92 fixed on a stub shaft 93which is journalled in the control panel 41. As shown in Figs. 4 and 5,the cam 92 is provided on its inner face 94 with a cam track 95 disposedto cooperate with diametrically disposed camfollowers 96 and 97,respectively.

, The cam follower 96 is carried by one end of a shifting arm 101 thatis journalled by means of a forked portion 7 extends between the gears55 and 56 of the couplet 49 in the primary shifting element and isoperative on movement of the shifting arm 101 bythe camgroove 95 actingupon the cam follower 96 to shift the gear 55 or the gear 56 intomeshing engagement with the respectively cooperating gears 57 or 58 ofthe idler cluster 60.

The cam follower 97 is carried on one arm of a bell ,crank shiftinglever 106 journalled by means of a forked arm 1017 on the inside of thecontrol panel 41 and that engages with the end of its other arm 108 ashifting fork 109 alsoslidably mounted on the guide rods 104 and 105, asshown in Figs. 4 and 5. The shifting fork 109is-generally similar to thefork 103 and is engaged in an annular groove formed in the hub of thecouplet 47 in the primary One complete revoluelement for shifting thegears 46 or 50 into engagement with the gear 51 or the gear '52,respectively of the idler cluster 60. As shown in Fig. 5, the cam grooveis sleeve 64 constituting the secondary element of the variable speeddevice A, there is provided a secondary cam 112 secured to a sleeve 113,Fig. 4, journalled by means of a bearing 1-14 on a stub shaft 115secured to the inner side of the control panel 41 directly-above andparallel with the shaft 93. The secondary cam plate 112 is opcrativelyconnected with the primary cam plate'92 by means of intermittent gearingconstituting a Geneva movement arranged in such a manner that the camplate 112 is turned through one-half of a revolution at the end .of eachcomplete revolution of the primary cam plate 92. As shown in Figs. 4 and5, the cam plate 92 is provided on its periphery, besides but spacedfrom the gear 91, with a discontinuous gear element 116, the teeth ofwhich mesh with a mutilated gear 117 secured on the outer end of thesleeve 113 and cooperating in a manner to effect the desiredintermittent movement of the cam 112 secured thereto.

As shown in Figs. 5 and 6, the secondary cam plate 112 is provided inthe inward face thereof with a cam track 118 that is engaged by camfollowers 119 and 120. The cam follower 119 is secured to a shiftingfork 121 lower is secured to shifting fork 124 which is also slidablymounted on the guide rods 122 and 123 for longitudinal shiftingmovement. The forward ends of the shifting forks 121 and 124 aredisposed to engage annular grooves 125 and 126 formed on the hubs of thegears 65 and 66 of the secondary elementfor respectively shifting.eearmg mterconnee i g 2'1 with the cam plates 92 and .1-12 is soproportioned that;.for. a h revolut n o the k. onoof th gears thevariable speed deviceA is shifted'to effect a change Tf or one speed tthe ext There ore. gh v lutions itheicrank 21 are required to effect allof the eight combinations of gearingavailable and which-result from [ofordinately rota ing th prim y e n Pl te 92. t r ftwo' cornpleterevolutionsand the secondary cam plate l lith oug o e revo t n- Forshittin t sear 7. of th r ediate ran Qchanger B. in coordinatedrelationship with the shiftable Head i ht e spee changing devi A.igthere is "p ovideda tertiary camplate (130 rotatably journalled on 1a.jhshaftliil secured to the inner side ofthe cover plate 41in, parallelrelationship to the stub shafts 93 and {115. cam plate 13.0 is alsooperatively connected with thev cam plate 92 by means of intermittentgearing constituting aGeneva movement arranged in such a f rnannerthatthe cam plate 130 is rotated through oned, of arevolution at the end ofeach two full revoluns oftheprimary cam plate 92. As. shown in Figs. 4;a d 5, the secondary cam drive sleeve 113 carries a dis- .c nttnuous.gear element .132, the teeth of which mesh ;with a mutilated gear 133carried by the tertiary cam plate .1130 and cooperating in manner toeifect the desired e mi tentmove e h v[I-he, tertiary cam plate 130 isprovided in the inner fa c erithereof, with, a cam track 134 that isengaged by a, follower 135. The cam follower 135 is secured to a hi insa m .36 wh ch a -en i al d'on .stuhshaft 137 secured to. the inner sideof the control 232d. 4 The opposite end of the shifting arm 136 is'arra1iged .to engage a shifting fork 138, slidably mounted forlongitudinal shifting movement on a guide rod 139 foamed by the speedbox 39. The forward end of the .ohifiing fork 138 is disposed to engagean annular groove 140 formed on the hub of the gear 74 for effectingleftwardmovement of the gear 74 into meshing engagement the cooperatingdriving ear 75, or for eifecting rightiWaHLInQYement of the gear 74 inmanner that the internal ,gean 7.6, formed therein is in engagement withthe gear 71. Q I. Ashereinbefore indicated, eight revolutions of thecrank ;are necessary to position the shiftable gearing in the .speedchanging device A for obtaining the eight stepped speed ratios availabletherethrough. A total of twenty- .four revolutions of the crank arerequired to obtain the three repetitive series of shifting movements ofthe gearcontained within the speed changing device A in order torohtainthe complete series of twenty-four speed ratios ohggii otthei e cluster1% r available with a coordinated positioning of the speed 111 Order toeffect a coordinated positioning of the range' changer B with a selectedpositioning of the speed changingdevice A, the gearing interconnectingthe crank 21 the cam plate .130 is so proportioned that for twentyfourrevolutions of the crank 21, the cam plate 130 is rotated through onecomplete revolution.

Forrthe first eight revolutions of the crank, coinciding with one seriesof eight shifting movements of the speed ehanging device A, the camplate 130 is rotated through one-third of a revolution during which timethe gear 74 is in engagement with the gear 75. At the completion ofeight revolutions of the crank 21, the cam track 1340f the tertiary cam130 and its cooperating follower 135 opcrate 1110 move the arm .136rightwardly in a manner that the internal gear 7 6 formed in the gear 74is shifted right- Wardly into engagement with the complementary gear 71.

the speed sel c crank 10 tion and the gearing in the. speed changingdevice adjusted through two complete series of shifting. movements.

In order to effect shiftable adjustmentof the range changing mechanismC, there is provided the independent- 1 ly movable range change lever 20secured to a shaft 144 journalled in the control panel 41, as shownin-Figs. 4 and 5. A shifting crank arm 145 secured. to the inner end ofthe shaft 144 is disposed to engage with its outer end a vertical groove146 formed in a fork 147 which is slidably mounted for longitudinalshifting movement on the guide rod 139. The forward end of the shiftingfork 147 engages an annular groove formed in the hub of the couplet 78and is selectively movable to effect shifting movement of the gears 80and 81, constituting the couplet into meshing engagement with thecooperating spindle driving gears 83 and 84, respectively.

In order to obtain the three driving ranges required for the completeseries of twenty-four spindle driving speeds available, the range changelever 20 is so posi- I tioned that the low range gear 80 meshes with thespindle driving gear 83 during the first sixteen revolutions of thecrank 21. For the last eight revolutions of the crank 21, the lever 20is shifted to effect meshing engagement of the high range gear 81 withthe spindle driving gear 84. For positioning the range change leverafter. it has been turned to shift the gearing, the lever 20, as shownin Figs. 1 and 4, is provided with an operating knob 149 and latchingdevice constituted by a spring pressed latching plunger (not shown) thatis adapted to enter locating holes 150 or 151 in the control panel 41and that provides for securing the lever 21 in a low or high rangeoperating position respectively.

In a similar manner, for retaining the speed selecting crank 21 in apredetermined coordinated position of adjustment with the range changelever 20, the crank 21 likewise is provided with an operating knob 153and latching device constituted by a spring pressed latching plunger 154that is adapted to enter a locating hole 155 in a stationary memberconstituting part of the control p-anel- 41,

as shown in Figs. 1 and 4. i r

The speed indicating device or dial 24 is mounted for rotation in thecontrol panel-41 concentrically with/the speed selecting crank 21 andcarries a continuous circular indicating scale constituted by speedindicia 15.6 arranged in approximate geometrical progression. As, shown,in Fig. 4, the indicating dial 24 has secured to its inner side a ringgear 157 which meshes with a cooperating pinion 158 secured to the.outer end of the primary cam operating shaft 93 whereby the speedindicating dial is operatively connected with the speed selecting crank21 for movement in predetermined coordinated relationship With the gearshifting control cams 92, 112 and 130.v The gearing interconnecting thedial 24 with the crank 21 is so proportioned that twenty-fourrevolutions of the crank are required to effect one complete revolutionof the dial. Each turn of the crank 21 effects an incrementaladvancement of the dial 24 corresponding to one of the twenty-four speedindicia 156 into which the continuous circular indicating scale carriedthereby is divided. For determining the selected spindle operating speedeffected by a combined positioning of the range change lever 20 and thespeed selecting crank 21, the speed indicating dial 24 is arranged tocooperate with one or another of the diametrically opposed indicatingplates 22 or 23 formed on the hub of the lever 20. The range changeplate 23 indicating the low range position of the lever 20 is preferablycolored to conform to the color of the speed indicia divisions on thedial 24 indicating the lower sixteen spindle operating speeds. 22indicating the leftwardly shifted or high range position of the rangechange lever 20 is likewise colored to conform to the divisions-on thedial 24 indicating the eight highest spindle operating speeds. With therange change lever 20 positioned as indicated in Fig. 1, the low rangeThe plate an les 'sp eed' 'plate 23 is adaptedto cooperate withthelfirsts'ix- 'jt'een of the 'indici'a 24' for indicating the sixteenlowest spindle speeds.

With the speed change crank 21iadjusted to position one or another ofthe five indicia '(withw provided with an inching control button 159, aswell as a spindle start button 180, and a spindle stop button 243, shownin Fig. 1, and which are operative to selectively control theenergization of the motor 18 as fully explained in the aforementionedPatent'No. 2,7 3 6,243.

In order to provide a uniform rate of spindle rotation at any of thespeeds available by a coordinated adjustment of the range change lever20 and the speed selecting crank 21, a heavy flywheel 162 is secured tothe rearward end of the spindle 16, as is shown in Fig. 2. The flywheelfunctions to reduce to a minimumrany slight fluctua tions of spindlespeed which might occur, for example, at the moment of impact as anindividual cutting tooth of a cutter (not shown) mounted on the spindle16 enters a workpiece carried by the table in the performance of acutting operation. 7

To properly center and position the flywheel 162 on the spindle 16, therearward end of the spindle is provided with a slight taper 163 disposedto cooperate with a complementary internal taper formed toward the innerend of a bored hole extending throughthe flywheel. For 7 securing theflywheel to the spindle, the spindle 16 is provided with a splined endportion 165 disposed to receive a locking plate 166 having acomplementary splined opening and secured to the flywheel by means ofcap screws 167 and dowels 168. A locking nut 169 is thread- 1 ed on therearward end of the spindle 16 in a manner to "retain the flywheel inlocked engagement therewith.

The knee 13 issupported in any selected position of I verticaladjustment by means of an improved elevating ly extending base section262 of the column 12 and reknee is connectable to effect synchromzedmani iall'y 605-. ,trolled rotationiof the spaced apart elevating screws.(not

shown) contained withinthehollow telescoping housin mea t-1264. I

1 In a modified form ofthe variable speed transmission v mechanism fordriving the tool spindle 16,-shown Fig. f 3,.the rangechange mechanismCis so arrangedgas to provide for mounting a flywheel 421. on thespindle '1'6 immediately within the forward wall of the column 12.

A principal advantage afforded by this construction arises from the factthat placing the flywheel 421 as close as possible to the tool retainingend of the spindle 16 reduces to aminimumthe deflectioncaused bytorsional stress in the spindle 16 in rotating a tool to perform acutting operation on a workpiece.- To rotate the cutter spindlc 16 at aselected speed in a low, intermediate or me high 1 speed range, theintermediate range changing mechanism B and the range changing mechanismC are coordinately operable on adjustment of thespeed selecting lever 21and the range change lever 20 to transmit power-from the coordinatelyadjustable speed changing device A-for rotatablydriving the tool spindle16 at aselected oneof spectively. contained within a pair of telescopingprotecv tive housing 263 and 264, as shown in Fig. 1.

To retain the upper surface 392 of the knee in a' plane .thatis at rightangles to the front face 293 of the column, Fig. 1, regardless of itsvertically adjusted position therealong, and to prevent any deviation inthe parallelism of the upper knee surface 392 relative to apredetermined horizontal plane, the elevating screws (not shown) aredisposed to be engaged at the same relative height above the columnbase'262 by a pair of cooperating internally threaded nuts (not shown).

For effecting manual adjustment of the knee 13, the saddle 14 and thetable 15 independently of the selectively connectable power drivenmeans, there are provided individually and separately operable manualcontrol means, as shown in Fig. 1. For effecting longitudinal movementof the table 15, a handwheel 380 at the leftward end thereof isselectively connectable to effect rotation of a table screw (not shown)journalled at its opposite ends in a pair of depending end brackets 371and 372 secured tothe opposite ends of the table 15. For

effecting cross'traversing movement of the saddle 14, that is providedwith a dovetailed guideway 395 slidably e11 gaging a complementaryguideway formed in the upper face of the knee 13, a handwheel 381 at thefront of the knee 13 is selectively connectable to effect manualrotation of a cross traversing shaft (not shown) relative to acooperating nut (not shown) carried by the knee 13. To

; effect vertical adjustment of the knee 13 relative to the column 12, acrank 382 journalled at the front of the change lever 20.

twenty-four driving speeds, as hereinbefore explained.

The speed selecting lever 21, Fig. 1,- is operative to shiftablyadjustthe speed changing device A, Fig. 3, coordinately with the intermediaterange changing mechanism B for transmitting driving power from the inputbevel gear 36 to rotate thedriving shaft 62, immediately below drivingshaft 62 to drive the spindle in a low or a high 7 range selectively.During the first sixteen revolutions of s the speed selecting crank 21,Fig. l, the rangechang'e lever 20 is retained in its low range drivingposition, and

for the last eight revolutions of the crank 21, the range change lever20 is moved to its high. range position for driving the tool spindle 16through its complete range of twenty-four driving speeds.

As shown in Fig. 3, the modified form of the'range changing mechanism Ccomprises a high s'peeddriving helical gear 422 rotatably journalled onthedriveshaft 62 and disposed to be in constant meshing engagement witha complementary helical gear 423' splined on the' spindle 16 incombination with alow speed driving pinion 424 slidably splined on thedrive shaft 62. Fordriving the tool spindle 16 in the low range, the lowrange driving pinion 424 is shiftably adjusted ,to its extreme rightwardposition on the shaft 62, as shown in Fig. 3, in a manner to meshinglyengage a low range gear 425 integrally formed with theflywheel 421 whichis splined directly to the spindle 16.. For driving the tool spindle 16in the high range, the low range pinion 424 is shifted leftwardly inmanner that the leftward end thereof engages an internal gear 426 formedin the high range pinion 422, thereby locking the pinion to the drivingshaft 62 for rotation therewith. Since the high range pinion 422 is ofthe helical typedisposed to be in constant meshing engagement with thecomplementary helical gear 423 splined to the spindle 16, engagement ofthe low range pinion 42 4 with the internal gear 426 formed in thehelical pinion 422 will effecttransmission of power from the drivingshaft 62 to rotate the tool spindle through its high range-of operatingspeeds. To adjust the range changing mechanism C for driving the toolspindle 16 in the high range or in the low range of speed selectively,there is provided on the low range pinion 424 an annular groove disposedto be engaged by a shifter fork 427 operatively connected to beshiftably adjusted by means of the range Fromthe foregoing explanationof the construction operation of the preferred embodiment oftheinvention,

transmission and control mechanism for' a milling machine fnisjincorporated with equal advantageltovdrive-the Work supstructures, orinfthe power transmisison; mechaany-lother movable member of'a machinetool Althoughiparticular-structures have been shown and .describcdinconsiderablc detaill as exemplary of the manlnwh icli theinvention maybepracticed, it will-be apparent'to' those skilled in the art to whichthis invention rqlates that various. modifications of, the structuresherein ,1 wn be efieet edwithout depaltingifrom the spirit and ppe-ofthefi nvention as defined in the subjoined clams.

: principles of the. invention having now been fully explained inconnectionwith the foregoing description of embodying structure, wehereby claim as-our invention:

1. ha variable-speed driving mechanism for a milling machine, atoolspindle disposed to be driven at a selected spejed' throughout awide selection of high and low speeds, a rotatabl'y journalled. shaftdisposed in parallelism with said tool spindle, a. sleeve journailed onsaid shaft for Iindcpndent rotation, range changing means including an 7element shiftablycarriedon said shaft disposed to transinit. powerbetween said shaft andsaid tool spindle at a Selected'bne of two drivingratios, an intermediate driving I including a driving. member shiftablycarried on said i shaftdisposed to transmit power from said sleeve todrive 1 said shaft at a. selected :one of two speed. ratios, a-speedchanging device including a pluralitywof motion transmittersshiftablycarried by said sleeve and, disposed to drive saidsleeve. at aselectedone of a plurality of driving:

, ingfplates cooperatively mounted and respectively actuatable onadjusting movement of said speed control mechanism and said rangechanger to coordinately indicate Qtiie selected output speed of saidtool spindle. 2. In a milling machine tranmission and control mech-:anism, a. driven member, a plurality, of range changing mechanismsconnected in series to drive said driven member in either a low,intermediate or high speed range, a speed changing mechanism connectedto drive one of said range changing mechanisms at one of a plurality ofstepped speeds within any one of said ranges, a power source connectedto'drive said speed changing mechanism at a predetermined constantspeed, a range change lever operatively connected toeflect shiftingmovement of one of said range changing mechanisms, a speed selectingcrank l, operatively connected to shift said speed changing mechanismand the other of said range changing mechanisms acoordinated manner, aspeed indicating dial carrying speedindicia associated with said speedselecting crank in a manner to be turned thereby to a plurality ofpositions corresponding to the various speed ratios efiected by shiftingsaid speed changing and said range changing mechanisms, and a rangechange plate associated with said range change lever in a manner to bemoved thereby into copperatin'g relationship with said speed indicatingdial to indicate the selected speed of said driven member.

3-. In-a variable speed mechanism for a milling machine,

. a tool spindle disposed to be driven at a selected speed a high orlalow range, a driving member operatively I connected to drive said toolspindle, a gear couplet slid- Y ablysplined on said driving member toconstitute a range changer and being shiftably. adjustable to transmitpower "14 a to v drive saidztool, spindle at one of two select d: ratiosa shiftinggear. ineluding, an. internal gear s-lidably. on," saiddriving member tot-constitute anv interme ate range changer andzbeingshiftablyadjustableto-drive. said driving memberatjone oi two selectedratios, an externally' splined sleeve rotatab'ly journalled on saiddriving member arranged-to. be driven at .one ota. pluralityvnfspeed-rates and constituting a source of driving p'owcr fgr saidinterinediaterange, changer, a plurality of shiftahie gears and-idlergearsincluding a plurality of shiftabie gears slidably splinedonsaidsleeve to constitute a speed chang ng device. and being, shiftablyadjustable to drige said 'sleeveata selected one of a plurality ofdifferent speeds, a; range change, lever ,operatively connected toeffect shiftable adjustment of said range changenaspeed selectormechanism operatively connected to effect shiftable adjustment ofsaid-speed changing device, a shifting device includinga pivotable leveroperatively connected toibe; actuatedlby said speed selector mechanismfor shittabl y adjusting said intermediate range changercoordinately'with said speed changing device said shifting: device beingdisposed to retain said intermediate range changer in. one shiftablyadjusted position during one complete series of shifting movements ofsaid speed changing device and to retain said intermediate range changerin its other shiftably adjusted position during two additional completeseries of shiiting'movements of said speed changing device, and a pairof indicating plates respectively associated with said range changelever and said speed changing mechanism being individually movable tocoordinately indicate the shift'ablyvadjusted, positions of said a and ange c an er-t 4. In a, variable speedfdriving and controllrnechanism fora milling machine, a, driven member disposedtobe driven at a selectedspeed throughout a wide selectionpf driving speeds, airange changer, anintennediate v ll changer and a speed changing device connected inseries by saidspeed change crank, said shifting arm being arranged to,retainsaid intermediate range changer inone to drirvesaidmember at aselected speed, a rangechange lever operatively connected. to adjustsaid range changer, a speed change crank operatively connected.iZQtfiJdlllSt said speed. changing device throughout a plurality ofrepetitive of shiftable adjustments, a shifting arm operativelyconnected to, adjust said intennediate range ch n e n eing op rative yconnq d to be actuate of its adjusted positions during one series ofshiitab le adjustments. of said'speed changing device and Saidshiftingarm being operable, to retain. said intermediate range changer inanother of its, adjusted positions during other series of shiftableadjustments of said speed chanigingdevice, and indicating plateassociated with said range change lever in a manner to be moved therebyto indicate t adju t d pos t o of sa d an a er, d a 0- operating dialcarrying speed indicia markings associated with said speed change, crankand disposed to; be moved thereby into coordinated'relationship withsaid indicating pl to nd c e the ele d peed of said drive member.

5. In a variable speed mechanism for a milling mashine, a rotatable,cutter spindle disposed to be driven throughout a wide selection of highand low speeds, a flywheel having external gear teeth formed on itsouter periphery to constitutea low speed drive gear and being secured tosaid spindle inproximity to the tool retaining end thereof, saidflywheel being positioned as close as possible to the tool retaining endof said spindle in order to minimize torsional stress therein wheneversaid spindle is being rotated, a high speed spindle drive gear havinghelical gear teeth formed in the outer periphery thereof and beingsecured to said spindle adjacent to said shaft dispesedto be in constantmeshing engagement with estates one of two driving ratios, anintermediate range changer including a gear slidably splined on saiddriving shaft in a manner to be adjustable for driving said shaft at 'aselected speed ratio, an externally splined drive sleeve 'rotatably'journalled on said driving shaft operable to 'drive said intermediaterange changer, a plurality of shiftable gears slidably splined on "saidsleeve, and a power'driven speed changing device disposed to cooperatewith the said gears splined on said sleeve, whereby said sleeve may. bedriven at a selected one of a plurality of speeds and said spindle maybe driven at a selected speed in a low, intermediate or highspeed range.

6. In a speed changing mechanism, a rotatable tool spindle, a firstrange change mechanism operatively connected to drive said tool spindleat a low range or a high range respectively, an intermediate rangechange mechanism connected to drive said first range changer at a lowrange or a high range respectively, a shiftably adjustable power drivenspeed changer operatively connected to drive said intermediate rangechanger at a selected one of eight speed rates, a speed selectingmechanism including a rotatable speed selecting: crank I operativelyconnected. to eifect a continuous sequenceof three series of shiftableadjustments of said speed changer r and simultaneously therewith toefiect a coordinate shiftable adjustment of said intermediate rangechange mechanism, said speed selecting mechanism being operative toretain said intermediate range change mechanism in its low rangeposition during the first series of shiftable adjustments of said speedchanger and to retain said intermediate rangechange mechanism in itshigh range driving position dtu'ingboth the second and third series ofshiftable adjustments of said speed changer, and a range change shiftingmechanism operatively connected to V shiftably adjust said first rangechange mechanism to its low range position during the first two seriesof shiftable adjustments of said speed changer and to retain said firstrange change mechanism in its high range position during the thirdseries of shiftable adjustments of said speed changer.

7. In a milling machine, an upstanding hollow column, a tool spindlejournalled in said column, a high speed gear and a low speed gearsecured to the forward end of said tool spindle, a primary drive shaftjournalled in parallel spaced relationship to said tool spindle, ashiftable gear couplet slidably splined to the forward end of said driveshaft, said couplet being shiftably movable into t engagement with saidhigh speed gear or with said low speed gear for driving said spindle ata high range or a low range respectively, a drive sleeve rotatablyjournalled on the central portion of said primary shaft, a slow speeddevice journalled in spaced relationship'to said primary shaft, saidslow speed device being connected to be change gear, said crank beingconnected to retain said intermediate range change gear in its low rangeposition during the first complete series-10f shiftable adjustments ofsaid speed changer, said crank beingyconnectedto retain J saidintermediate range change gear-in its high range position during thesecond two series ofgshiftable adjustments of said speed changer, and arange change mechanism connected to shiftably adjust said shiftable gearcouplet to be driven bysaid slow speed gear during the first two seriesof shiftable'adjustments of, said speed changer and to be driven by saidhighgspeed gear during .the third series of'shiftable adjustments ofsaid speed changer.

8. t In a machine tool, a column, a tool spindle journalled in saidcolumn, a drive shaft journalled in said column in parallel spacedrelationship to said tool spindle, a

first shiftably adjustable range changer operatively connectable totransmitpower from one end of said drive shaft for rotating saidspindle'at a low 'or a high speed range, a second shiftably adjustablerange changer operatively connectable to drive the opposite end of'saiddrive shaft at a low or at a high speed range, an externally splinedsleeve rotatably journalled on the central portion driven by saidsleeve, an intermediate range change=gear slidably splined on therearward end of said primary shaft for axial shifting movement, saidintermediate range change gear being shiftably movable to be driven'bysaid sleeve or by' said slow speed device for driving said primary shaftat a high or a low range of speeds respectively, a shiftably adjustablespeed changer operatively connectable to drive said sleeve at a selectedone of eight speed rates, a motor connected to drive said speed changer,a shifting mechanism including a rotatable speed of said speed changerthrough' three complete series of speed selecting adjustments andsimultaneously therewith being connected to shiftably adjustsaidintermediate range to its high range position during the third series ofof said drive shaft and beingconnected to drive said secondrange-changer at a selected one'of ajplurality of speed rates, aselectively adjustable speed changer including a plurality of shiftablegears slidably splined to said sleeve for individual shifting movement,said speed changer being selectively adjustable for driving said sleeveat a plurality of speed rates, a speed selector including a rotatablecrank connected to effect a continuous sequence of three series ofshiftable adjustments of said speed changer, said speed selector beingconnected to retain said second range changer in its low range positionduring'the first series of shiftable adjustments of said speed changer,said speed selector being connected .to retain said second range changerin its high range-position duringrthe last two series ofshiftableadjustments, of said speed changer, and a range change selectorconnected to shiftably adjust saidfirst range changer, to'its 'lowfrangeposition during the first two series of shiftable adjustments of saidspeed changer, said range change selector being operative to shiftablyadjust saidfirst range changer shiftable adjustments ofsaidspeedchanger. a

9. In a machine tool, a column, a tool spindle journalled in saidcolumn, a primary driving shaft journalled in said column in parallelspaced relationship to said tool spindle, a power driven speed changingmechanism carried in said column, a sleeve rotatably journalled to ro-'tate on the central portion of said primary driving shaft, said sleevebeing connected to be drivenat' a selected speed'rate by said speedchanging mechanism, an intermediate range changer. including a shiftablegear slidably splined toward one end of said primary driving shaft,

, saidintermediate range changer being voperatively connectable to,transmit power from said sleeve for rotatably driving said primaryshaftat a selectedrange ofspeeds,

and a second range changer including ashiftable' gear 'slidablysplinedto the opposite end of said primary driving shaft, said second rangechanger beingvselectively connectable to transmit driving power fromsaid primary Shaft f or driving speeds.

said tool: spindle at a selected range of 10, In"a machinetool, acolumn, a driven member journalled in said column, a driving memberjournalled selecting crank connected to eflFect shiftable adjustment insaidicolumn, a sleeve journalled to rotate ,on said driving member, ashiftably adjustable'power driven' speed chang'erconnected to drive saidsleeve at "a' selectedone of eight speed'rates, a first range changeroperatively connected to'transmit driving power from said sleeve torotate said driving member sat a selected 'one of two speed ranges, asecondrangechanger connected to transmit power from said drivingmember'at a selected 1 f .tWospeed ranges,'a speed selecting mechanismconnected to efiect a coordinated shiftable adjustment of said speedchanger and said first range changer, and a range changing mechanismconnected to effect a selective shiftable adjustment of said secondrange changer.

11. In a variable speed transmission mechanism, a rotatably journalleddriven member, a rotatable driving member journalled in spaced apartrelationship to said driven member, a first shiftable range changeroperatively connectable to transmit power from one end of said. drivingmember to rotate said driven member at a selected one of two speedranges, a second shiftable range changer operatively connectable to theopposite end of said driving member for rotating said driving member ata selected one of two speed ranges, an externally splined sleevejournalled to rotate about the central portion of said driving memberintermediately said range changers, a speed changer including'a pair ofshittable gears 'slidably splined to said sleeve for axial shiftingmovement, said speed changer being connectable to transmit power forrotating said sleeve at one of a plurality of eight different 18 speedrates, a motor connected to drive said speed changer, a shiftingmechanism operatively connected to efiect a coordinated shiftableadjustment of said speed changer and said second rangeehanger, and asecond shifting mechanism connected to effect selective shiftableadjustment of said first range changer.

References Cited in the file of this patent UNITED STATES PATENTS2,008,983 Kearney July 23, 1935 2,110,173 Pohl et a1. Nov. 8, 19382,164,884 Nenninger et a1 July 4, 1939 2,214,805 Baker et a1 Sept. 17,1940 2,303,270 Grover Nov. 24, 1942 2,338,121 Le Blond et a1. Jan. 4,1944 2,349,595 Marlellotti May 23, 1944 2,505,221 Tomlinson Apr. 25,1950 2,597,716 Eserkaln May 20, 1952 2,706,544 Schuman Apr. 19 1955

